A plasma coil is a component of a starship's engines.
The D12 class Klingon Bird-of-Prey was retired from service as its plasma coils were defective. (Star Trek: Generations)
While visiting Deep Space 9 in 2369, Geordi LaForge was interested in purchasing a 21st century Ktarian plasma coil that he found in a shop on the Promenade in near perfect condition. (TNG: "Birthright, Part I")
Loose plasma coils create large amounts of radiations. A Bajoran transport docking at DS9 in 2372 had a loose plasma coil, preventing the station from beaming off wounded passengers. (DS9: "Life Support")
Fluctuations in the plasma coils can cause a power surge in the warp core. When this occurs, the ship is typically required to take the core offline. (DS9: "Our Man Bashir")
See also: